First, strong parties with organic ties to their constituents do matter. I don't want to downplay that too much.

Second, it is tricky to use the Andean countries as an example of things falling apart. Bolivia and Ecuador actually stabilized dramatically under Evo Morales and Rafael Correa. Correa even stepped down voluntarily rather than give in to temptation (which of course Morales could not resist). Starting in 2006, when both Correa and Felipe Calderón were elected, Ecuador has become more stable than Mexico. In a 2016-2017 LAPOP survey, 20% in Ecuador trusted political parties compared to 13.8% in Mexico (Bolivia is also higher at 16.3%).

Third, the Mainwaring and Scully analysis is 1995 so cannot account for the drug war and associated organized crime, which connects to immigration as well. Mexicans are unhappy with corruption and violence, not the economic system per se. Incidentally, Bolivia suffered under the U.S. drug war too, and has been doing much better after turning to the Brazilians rather than the United States.

I don't have a firm conclusion here, except maybe that Mexico's current shake up isn't necessarily the end of the world. It's tough to compare to the Andean region because the history of parties there is so different, but they've been doing pretty well. Mexico, with its strong parties, has not.